Studies on the control of gene expression in eukaryotic cells is the primary objective of this proposal. Cellular DNA which carries the genetic information is transcribed into RNA in the nucleus and undergoes certain processing before it is transported into the cytoplasm for the ultimate process of translation into cell specific protein. Thus control of gene expression may be exerted by the modification of any one or more of these sequences of events starting from the step of complementary RNA synthesis from the specific nucleotide sequence of the DNA to the ultimate step of synthesis of a peptide molecule containing a specific amino acid sequence. The present proposal utilizes a system composed of functional pituitary tumor cells in culture (GH-cells). Studies on the control of expression of prolactin (PRL) and growth hormone (GH) genes in GH-cells has been proposed in this application. GH-cells synthesize and secrete into the medium these two hormones which are simple proteins having molecular weight in the range of 22000. The novel properties of GH cells in culture such as 1) production of large quantities of each hormone (about 10% of the total protein synthesis at the induced state), 2) response to externally administered physiological stimuli, 3) differential production of GH and PRL under the influence of different stimuli will be exploited to investigate plausible regulatory mechanisms involved in the expression of PRL and GH genes in GH-cells. The present proposal also utilizes the cell-free systems (i.e., cell-free nuclear system, and heterologous and homologous translation system) established by the PI for the study of nuclear and cytoplasmic events involved in the expression of a gene in eukaryotic cells.